Effect of Grapevine Training Systems and Pruning Practices on Occurrence of Phomopsis Cane and Leaf Spot. J. W. Pscheidt, Former Research Associate II, Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456. R. C. Pearson, Associate Professor, Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456. Plant Dis. 73:825-828. Accepted for publication 14 April 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0825.

Vitis labrusca ‘Concord’ vineyards with hand-pruned umbrella Kniffin trained vines, hand-pruned top-wire cordon trained vines, or hedged top-wire cordon trained vines were examined for incidence and severity of Phomopsis cane and leaf spot, caused by Phomopsis viticola. These vineyards were also evaluated for the development of pycnidia of P. viticola before budbreak. Vines that were hedged for 2 yr or more had significantly more disease than hand-pruned vines. No consistent difference in the duration of cane wetness or temperature during the wetting period could be detected between pruning systems from budbreak through bloom. Shoots at the 12.7-cm growth stage and clusters in bloom were spray-inoculated with 1 × 10⁷ alpha spores of P. viticola. Inoculated internodes from shoots of hand-pruned vines were more susceptible to symptom development than internodes from shoots of hedged vines. Leaves and clusters from both pruning types were of similar susceptibility, however. Bundles of 1-yr-old canes from severely infected vines in 1986 were tied above hand-pruned umbrella Kniffin trained vines before budbreak in 1987. The incidence of Phomopsis cane and leaf spot on leaves and internodes two to five from the base of the shoot and on summer lateral shoots increased significantly as the size of the bundles increased. In addition, the number of berries with symptoms of Phomopsis fruit rot was significantly higher on vines with 907-g bundles than on vines without bundles. Hedged vineyards were at a higher risk of disease development because of higher inoculum levels but not because of environmental differences or increased susceptibility. Growers who use mechanical cutter bars for pruning are encouraged to remove dead and infected canes or adopt a more comprehensive disease control program utilizing chemical eradication or protection.

Keyword(s): latent infection.